【摘要】 利用常规气象观测资料、NCEP/NCAR再分析资料等,对2008年7月中旬宁夏久旱转雨过程的环流演变及各种物理量场特征进行诊断分析。结果表明:干旱期宁夏上空长期维持稳定的"西高东低"环流型;大尺度环流形势的调整,特别是中纬度环流形势向"东高西低"转变,是久旱转雨的必要条件。进一步分析发现,这次过程是典型的西太平洋副热带高压(副高)北抬西伸型,副高584 dagpm外围的"SW"气流增强,也与高空冷槽、低空急流、低涡切变和不稳定层结(能量)的发展等有关;久旱转雨时水汽、热力、动力等物理量场的变化也较明显,降水产生在低层高能舌、水汽辐合带及低层辐合、高层辐散的上升气流区内。在此基础上,提出了宁夏夏季久旱转雨预报概念模型及预报着眼点。更多还原

【Abstract】 Characteristics of the circulation evolution and the physical quantity field of the process from drought to rain in Ningxia in 2008 are diagnostically analyzed,using the meteorological observation data,NCEP/NCAR reanalysis data and so on.The results show that there is stable circulation pattern of "high in the west and low in the east" over Ningxia for a long time during the drought period;the adjustment on large-scale circulation,especially the changing of mid-latitude circulation into the pattern of "high in the east and low in the west",is a necessary condition of the turning from drought to rain.With further analysis,it is found that the south flow on the west side of subtropical high is important,which means that the subtropical high strengthened and moves northward,the south flow on the west side of 584 dagpm of subtropical high strengthened and so on.Meanwhile the development of upper cold trough,lower-level jet,low vortex shear and instability stratification(energy) are also important.The variations of physical quantity field of water vapor,thermodynamic and dynamic variables and so on are relatively obvious when the weather change,and rain always occurs in the area with high energy tongue at the lower layers,the vapor convergence zone,and the updraft region with convergence at the lower layer but divergence at the upper layer.On the basis,the conceptual model for forecasting of Ningxia weather process from drought to rain in summer and the key points for its forecasting are put forward.更多还原